Era codes tracking issue

[robertbastian]

CLDR era codes are in flux and will change in CLDR 48. We need to make sure to update the test in source/src/calendar/eras.rs when we integrate 48.

[sffc]

The 2.0 goal here is to make sure what we have aligns with the latest agreement.

[sffc]

I sent an email to the TC asking whether we can consider this a non-breaking change and move it out of the milestone.

[sffc]

The next steps would be:

1. Update CLDR-18465 Remove Before Diocletian era from Coptic calendar cldr#4620 according to the era indices discussed today and then merge
2. Rebase CLDR-18369 Revise era codes to match Temporal specification cldr#4519, remove saka, minguo, minguo-qian, and before-roc, and put up for approval and merge

[robertbastian]

Me to update ICU4X to that^